In typical PTA or PTCA procedures, a guiding catheter is percutaneously introduced into the cardiovascular system of a patient and advanced through the aorta until the distal end is in the desired artery or vessel. Using fluoroscopy, a guide wire is then advanced through the guiding catheter and across the site to be treated in the coronary artery. A balloon catheter is advanced over the guide wire to the treatment site. The balloon is then expanded to reopen the artery. The catheter may have a guide wire lumen which is as long as the catheter (over the wire) or it may be a rapid exchange catheter wherein the guide wire lumen is substantially shorter than the catheter. Alternatively, a fixed wire balloon may be used. This device features a guide wire which is affixed to the catheter and cannot be removed.
To help prevent arterial closure, repair dissection, or prevent restenosis, a physician can implant an intravascular prosthesis, or a stent, for maintaining vascular patency inside an artery or other vessel at the lesion.
Stents are also used for a variety of other purposes including maintaining the patency of any physiological conduit including but not limited to arteries, veins, vessels, the biliary tree, the urinary tract, the alimentary tract, the tracheobronchial tree, the genitourinary system, and the cerebral aqueduct.
For the purposes of this disclosure stents and medical devices may be considered to include any stent, covered stent or prosthesis or any medical device system, grafts or biologic device.
The stent may either be self-expanding or balloon expandable. For the latter type, the stent is often delivered on a balloon and the balloon is used to expand the stent. The self-expanding stents may be made of shape memory materials such as nitinol or constructed of regular metals but of a design which exhibits self expansion characteristics.
In certain known stent delivery catheters, a stent and an optional balloon are positioned at the distal end of the catheter, around a core lumen. The stent and balloon are held down and covered by a sheath or sleeve. When the distal portion is in its desired location of the targeted vessel the sheath or sleeve is retracted in a proximal direction on the catheter to expose the stent. After the sheath is removed, the stent is free to self-expand or be expanded with a balloon.
In a stent deployment system which utilizes a retractable sheath, retraction of the sheath may result in inaccurate placement of the stent for a variety of reasons including, but not limited to, the interaction of the sheath and guide catheter upon retraction. One way of dealing with this is to make the retractable sheath long enough so that it will be contained in the guide catheter at all times. This increases system profile, reduces flexibility and creates excess friction upon sheath retraction.
Another way of dealing with this issues is described in commonly assigned U.S. Pat. No. 5,772,669. The stent delivery system disclosed therein comprises, in a catheter having a proximal outer shaft, a retractable distal sheath concentrically arranged around a stent receiving portion of the catheter and a pull back means operatively connected to the distal sheath. The catheter is further arranged so that the retractable sheath or a member connected thereto is pulled into the proximal outer shaft of the catheter during retraction of the distal sheath thereby freeing the loaded stent.
All U.S. patents and applications all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
Without limiting the scope of the invention in any way, the invention is briefly summarized in some of its aspects below.